This invention relates to an electrode catheter which is inserted into the body of a patient for an electrophysiological examination, especially to an electrode catheter for use in the electrophysiological examinations made prior to the therapies for tachycardiac arrhythmia such as WPW (Wolff-Perkinson-White) syndrome or paroxysmal supraventricular tachycardia.
The electrophysiological examination made prior to the therapies for tachycardiac arrhythmia is conventionally performed by using a plurality of electrode catheters whose structure is such that one or two to ten electrodes are secured to the outside surface of the distal end portion, and the lead wires of the electrodes are extended through the inside of the hollow catheter to the proximal end for connection to a measuring apparatus. In the electrophysiological examination for bypass pathway-caused arrhythmia such as WPW syndrome, the bypass pathway which exists in the annulus of cardiac valves must be located- Since a thick coronary sinus runs in the annulus of mitral valve, measurements in the left heart portion can be performed relatively easily by inserting the multi-electrode catheter into the coronary sinus. However, there is no thick vein running in the annulus of tricuspid valve in the right heart portion. The right coronary artery running in this area is thin, and hence it is difficult to insert the conventional multi-electrode catheter into the right coronary artery. If the catheter could be inserted into the right coronary artery, there is a danger of causing acute myocardial infraction by obstructing the blood flow. For this reason, measurements in the annulus of tricuspid valve is performed by inserting an electrode catheter with an electrode at the tip into the right ventricle and moving the measuring position one point after another, resulting in a very cumbersome examination which takes a few hours.
Since the conventional examination is performed by using electrode catheters equipped with a small number of electrodes as described above, it takes a long time to locate the bypass pathway accurately. On the other hand, electrodes must be disposed at large intervals in order to measure over a wide area in a short time by a catheter with a small number of electrodes. It is difficult to locate the bypass pathway accurately by such a catheter with a small number of electrodes disposed at large intervals. Further, it is also difficult to increase the number of electrodes of the conventional electrode catheter in order to solve this problem. If the number of electrodes is increased, the number of signal transmitting wires must also be increased, resulting in a larger outside diameter of the catheter which makes examination of the right heart portion difficult.
An electrode probe to solve the above problem was proposed by the same inventors as of this application in Japanese Patent Application Laid-Open No. 335460/1994.The electrode probe has a plurality of electrodes which are formed by winding 12 wires for signal transmission on a PTCA guide wire made of Ni-Ti alloy and removing the insulating coating of the wires at the distal end portion of the winding.
This conventional electrode probe (electrode catheter) is relatively easy to insert into normal blood vessels. However, when there are lesions such as aneurysm and arteriovenous teratoid tumor in blood vessels, an electrode catheter must be inserted to an intended position by way of complexly branched thin blood vessels. To be easy to insert into thin blood vessels, an electrode catheter must have a high pushability which faithfully transmits a move in the axial direction applied to the proximal end portion to the distal end, a high torque transmitting ability which faithfully transmits a turn around the axis applied to the proximal end portion up to the distal end, and a high kink-resistance which prevents the catheter from collapsing at a bend in a blood vesseL However, the conventional electrode probe does not have sufficiently high pushability and torque transmitting ability because of the insufficient rigidity of the center wire which is made thin, though it has a high kink-resistance.
In addition, to lay the wires inside the catheter tube, a process which forms holes in the wall of the catheter tube, passes the wires through the holes from the inside to the outside of the catheter tube, and connects the wires to their corresponding electrodes is needed. This process can be applied to conventional electrode catheters whose inner tube diameter is equal to or greater than 2 mm and whose have up to three electrodes, though the working is difficult. However, for an electrode catheter whose inner tube diameter is 1.5 to 1.0 mm or smaller and whose has three electrodes, as thin as a guide wire, it is very difficult to form holes in the wall of the tube and to pass the wires through the thus-formed holes.
Further, if the outside diameter of a conventional electrode catheter is reduced, the diameter of the inner tube also becomes smaller. When the outside diameter is 1.0 mm, for example, the inside diameter becomes 0.6 mm since the wall thickness of about 0.2 mm is required to be usable as a catheter If the diameter of the wires used is 0.1 mm and 20 wires are laid inside the catheter, the lumen of the catheter is almost fully filled with the wires. When a bending stress is applied to this catheter, the catheter bends and exerts a stress on the lead wires which almost fully filling the lumen. The catheter collapses when an excessive bending stress is applied, exerting a greater stress on the wires. Since the wires almost fully filling the lumen of the catheter, deformation of the catheter exerts a stress on the wires, and the wires can break in the worst case.
The strength of the catheter decreases to provide the plural holes (especially, above four electrodes) to pass the wires to a catheter. The catheter may be broken at a part of the catheter provided many holes. This invention has been made in consideration of the above conventional electrode catheters. The object of this invention is to provide an electrode catheter whose number of electrodes can be increased without increase of the diameter, the problem with the conventional electrode catheter, and which has a high torque transmission capability, flexibility, and kink-resistance.